The support of the hanging wall in stopes is one of the most basic requirements in underground mining. Dependant on the type and quality of rock being supported, the depth of mining, the prevalent field stresses, seismicity, stopping width and a number of other factors, stope support can vary across a vast range of materials, configurations and systems. These include, amongst others, timber poles, timber and composite packs, steel props, unmined pillars, rock and granular or tailings type supports.
Among the granular support media, cemented grout packs are being increasingly used as combination support products. These consist essentially of a support column formed by cured cemented backfill, or other suitable cured cementitious grout, contained within a bag usually made of a geotextile material, which is stiffened against lateral deformation under axial load with external restraining rings. These are commonly referred to as “grout packs”.
At present, grout packs are typically used in association with external timber elongate supports which are used to clamp a support net or restraining ring assembly against the hanging wall during erection and filling of the grout pack. The geotextile grout bag of the grout pack is suspended within the restraining ring assembly ready to receive pumped grout. After inflation of the grout pack the support elongates are left in place and become part of the pack assembly contributing to some extent to the compressive resistance of the pack.
However, as the pack dilates under vertical compression the support elongates may become deflected sideways thereby losing at least some of their effectiveness as complementary hanging wall supports. Also, the support elongates, in the event that they are of timber, represent a fire hazard and, furthermore, they simply represent additional physical obstructions.